Joist questions
Joist questions
(OP)
Bottom chord extensions: I always show b.c. extension when the joist is bearing on a column. Otherwise if the architect does not ask for the extension to support the ceiling, I don't ask for it either. From what I understand, you need bottom chord extensions when the joist is part of a frame and resists axial loads. Any input?
Camber for long span joists: Say I have a 70' long 40LH roof joist. Who decides how much camber should be there in the joists. Should I as engineer dictate LL deflection (say L/240 or L/360), indicate the loads and let the jst mnfr decide what the camber should be or should this info be on my design documents?
Thanks.
Camber for long span joists: Say I have a 70' long 40LH roof joist. Who decides how much camber should be there in the joists. Should I as engineer dictate LL deflection (say L/240 or L/360), indicate the loads and let the jst mnfr decide what the camber should be or should this info be on my design documents?
Thanks.






RE: Joist questions
1. You are correct that joists as part of a frame (or resisting axial load) will need to have bottom chord extensions at the columns.
2. If you look in the Vulcraft Joist catalog they have tables for approximate cambers of joists. However, if you will have special situations where stricter deflection criteria will need to be used (brick, folding partitions etc....) It would be in your best interest to provide a joist diagram with the loads and design criteria you would like them to follow. Camber is their deal let them design for it.
Hope that helps!
RE: Joist questions
Licensed Professional Engineer (Illinois)
RE: Joist questions
Dik
RE: Joist questions
BA
RE: Joist questions